Microwave-resonator and measuring device

ABSTRACT

A resonator device for testing a material quantity in the tobacco-processing industry for existence of at least one foreign substance and/or for detecting at least one of weight, density and humidity level of the material includes a resonator housing having a through opening for the material to pass through and a testing region located inside the resonator housing to which the material can be moved at least in part. The device has at least one element that increases energy density of electromagnetic waves for increasing the energy density in at least a portion of the testing region.

CROSS-REFERENCE TO RELATED APPLICATION

Priority is claimed herein with respect to German Patent ApplicationSerial Nos. 101 12 499.6 filed on Mar. 15, 2001 and 101 57 266.2 filedon Nov. 22, 2001, the subject matter of which, along with the subjectmatter of each and every U.S. and foreign patent document mentionedherein, is incorporated herein by reference.

BACKGROUND OF THE INVENTION

The invention relates to a resonator device, in particular a microwaveresonator device, for testing a material quantity and especially amaterial flow in the tobacco-processing industry for the existence of atleast one foreign substance and/or for detecting the weight, densityand/or humidity level of the material or material flow. The resonatordevice is provided with at least one resonator housing and at least oneopening in each resonator housing for the material or material flow topass through.

The invention furthermore relates to a corresponding measuring device,especially a microwave measuring device, as well as a measuring system,in particular a microwave measuring system, for testing a materialquantity and especially a material flow in the tobacco-processingindustry for the existence of at least one foreign substance and/or fordetecting the weight, density and/or humidity level of the material.Such a measuring device comprises at least one resonator housing, insideof which an electromagnetic field can be generated and which has atleast one through opening for the material.

Finally, the invention relates to a method for testing a material forthe existence of at least one foreign substance and/or for detecting theweight, density and/or humidity level of the material.

A corresponding resonator device or resonator housing for microwaves isknown from German Patent No. 198 54 550 A1 commonly owned by the presentassignee. This document discloses a resonator housing for thetobacco-processing industry, through which a rope of tobacco is movedand is subjected to microwaves for the purpose of detecting the weightand/or humidity level of the rope material. The purpose of thisresonator housing is to improve the measuring accuracy and, ifnecessary, the measuring sensitivity when detecting the weight and/orhumidity level of filler materials for ropes in the tobacco-processingindustry. According to German Patent No. 198 54 550 A1, this is achievedby producing the housing at least in part from a material with a lowexpansion coefficient, so that with a corresponding fluctuation in thetemperature, the housing essentially retains the same shape. It alsoimproves the measuring accuracy if the resonator housing temperature iscontrolled to be at a constant value. Finally, it is advantageousaccording to the aforementioned reference if the interior housing wallsare at least partially coated with a corrosion-resistant metal orconsist of such a metal. The measuring accuracy for detecting the weightand/or humidity level for the aforementioned materials can be improvedconsiderably in this way.

German Patent No. 101 00 664.0 also commonly owned by the presentassignee, furthermore discloses a method for testing a productionmaterial or a material quantity primarily containing a productionmaterial, wherein the material is tested for the existence of a foreignsubstance. A microwave field is generated for this, the material ismoved into the effective range of the microwave field and its influenceon the microwave field is analyzed, wherein the actual values of a firstand a second characteristic variable of the microwave field are measuredsimultaneously. A reliable value range is specified for these actualvalues and these are checked to determine whether the actual values arein the reliable range. A signal is generated if the actual values areoutside of the reliable value range. For the purpose of this invention,the variable for a microwave field includes real variables of thegenerated microwave field, such as amplitude and phase, as well asvariables of the components for guiding a microwave field, e.g. theresonance frequency and the band width of a resonator in which themicrowave field propagates.

With the known measuring method, the goods to be measured are movedthrough the field of a resonator, wherein the dielectric properties ofthe goods to be measured change the field. By measuring the change inthe resonance properties or the field, it is possible to determine theweight, density and humidity level as well as to detect foreignsubstances. However, it is difficult to detect very small foreignsubstances or to achieve a relatively exact local resolution. Inparticular the position of the foreign substance relative to the fieldorientation determines the measuring accuracy.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a resonator device,a measuring device and a measuring system, which increase thesensitivity of a method for determining whether a material flow containsa foreign substance and/or for detecting the weight, density and/orhumidity level of the material flow or the material quantity.

Furthermore, it is an object of the present invention to increase thesensitivity of such a method and, in addition, provide means and amethod for improving the accuracy and the local resolution of respectivemeasurements.

The above and other objects are solved with a resonator device, inparticular a microwave resonator for testing a material, in particular amaterial flow, in the tobacco-processing industry for the existence ofat least one foreign substance and/or for detecting the weight, densityand/or humidity level of the material or the material flow. Theresonator device comprises a housing provided with an opening for thematerial quantity or the material flow to pass through, wherein thematerial can be transferred at least in part to a testing area, locatedin particular inside the resonator. At least one element that increasesthe energy density of electromagnetic waves is provided, wherein theenergy density can be increased at least in a portion of the testingarea.

As a result of this measure, a kind of bundling of the electromagneticwaves is possible in the testing area, which results in an increasedflow of the respective waves, in particular microwaves, through thematerial to be checked or the region of the material flow to be checked.As a result, the sensitivity when measuring the weight, density and/orhumidity level of the material flow and/or when testing for theexistence of a foreign substance is increased, without the necessity ofcoupling additional energy into the resonator device. For the purpose ofthis invention, increasing or raising the energy density ofelectromagnetic waves in particular also means that these waves arebundled, focused, narrowed down or compacted. The electromagnetic wavespreferably are microwaves. A material is advantageously tested with theresonator device according to the invention. The material advantageouslyis a material flow. For the purpose of this invention, the term testingregion also encompasses the term measuring region.

The element preferably comprises a line resonator with at least one endface functioning as electrode. By using a line resonator, the wavescoupled into the resonator can be bundled easily and effectively,wherein the waves or the respective field in particular exit the endface in the form of a beam.

It is advantageous if a coupling-in antenna and a coupling-out antennaare provided, which are arranged symmetrically inside the resonator. Theantennas are furthermore arranged near a spot on the line resonator,where the field component that induces the coupling has a highamplitude, preferably a maximum.

A particularly good coupling of the waves coupled in and out of theelement occurs if the element is preferably arranged inside a resonatorcavity, at a distance to the walls delimiting the cavity.

A particularly effective method for testing the material flow ispossible if the at least one end face is arranged near the material flowor the material quantity or the testing region. The size of the end facepreferably is smaller than the region of the material flow, locatedinside a testing region in the resonator, wherein a cross-sectionalsurface that is essentially parallel to the end face is taken intoconsideration. The material flow, which in this case is a tobacco flowin the tobacco-processing industry that is advantageously wrapped with awrapping material such as paper, refers to a cigarette rope having acircular diameter of approximately 6 to 10 mm. The size of the end face,which may be rectangular, is preferably smaller than {fraction (1/10)}of the area for the material flow to be projected against one wall ofthe resonator device. This refers, for example, to an area ratio asshown in FIG. 2, wherein the decisive area is the cross-sectionalsurface of the cigarette rope inside the cavity 7, which is shown inFIG. 2.

The line resonator preferably is a metal strip or a thin metal cube withan end face in the direction of the testing region. If at least oneinside wall of the resonator housing preferably serves as an electrode,particularly as a backplate electrode to the end face, theelectromagnetic wave field can be generated between the end face of themetal strip and the inside wall, so that a defined, narrowly limitedmeasuring range is provided.

Two end faces are advantageously provided, which are directed toward thetesting region. A particularly preferred embodiment of the resonatordevice has two end faces, wherein these are arranged opposite each otherto allow the material flow to move through the space between the endfaces. Such an embodiment of the resonator device permits a particularlyeven bundling of the waves, wherein an extremely high energy density ispossible. The line resonator preferably is an open ring. In addition,the two end faces preferably are essentially parallel to each other,which further increases the homogeneity of the wave field.

Extremely reliable and exact measurements are possible if the oneelement consists at least in part of a material with low expansioncoefficient, especially with respect to temperature. A long service lifeis ensured for the resonator device if the at least one elementfurthermore is coated with a corrosion-resistant material and inparticular a metal and/or consists in part of such a material.

The invention further provides for a measuring device, in particular amicrowave measuring device, for testing a material, especially amaterial flow in the tobacco-processing industry, for the existence ofat least one foreign substance and/or for detecting the weight, densityand/or humidity level of the material. The invention comprises at leastone resonator housing, which is provided with at least one opening forthe material to flow through and inside of which an electromagneticfield can be generated. The invention is modified in that the measuringdevice comprises at least two resonator housings, which respectivelydefine one measuring range, wherein each electromagnetic fieldrespectively comprises an electric field and the fields in therespective measuring regions are oriented in different spatialdirections relative to each other. The electromagnetic field in thiscase is preferably a microwave field, comprising a stationary microwavefield in the resonator housing. According to the invention, thedifferent directions, relative to each other, of the electrical fieldspermit a more exact determination of foreign substances since foreignsubstances not detected with the one resonator housing can be detectedwith a high probability with the other resonator housing. In particularthis refers to foreign substances having a geometric shape that islarger in one direction than in the other direction. Having differentfield directions relative to each other in space means, in particular,that these fields are distinguished by different angles relative to theconveying direction.

The measuring regions preferably are positioned successively in aconveying direction of the material flow, so that a separate evaluationof the respective measurements of the material quantity in the measuringregions can take place and so that the individual measuring regions arenot influenced by the adjacent measuring region.

A particularly preferred embodiment of the present invention is obtainedif the electrical fields are oriented essentially orthogonal to eachother. For the purpose of this invention, orthogonal means perpendicularto each other.

If one electrical field is oriented essentially in the conveyingdirection of the material flow and one electrical field is orientedcrosswise thereto, it is possible to take a measurement in thetraditional manner, for example as described in German Patent No. 198 54550 A1, as well as take a supplemental measurement crosswise to thisdirection.

For the purpose of this invention, field refers in particular to anelectrical field. In the case of a dynamic field, the field intensityvector represents one field direction or orientation, as for astationary electromagnetic wave.

If three resonator housings are provided, the measuring accuracy can beincreased even further. For this, the third resonator housing ispreferably designed so that the electrical field is positionedessentially orthogonal to the fields inside the other two resonatorhousings.

The measuring device according to the invention preferably comprises aresonator device that is designed or advantageously equipped accordingto the invention, as described in the above. A compact design for themeasuring device is obtained if a single housing comprises at least tworesonator housings.

According to a further aspect of the invention, there is provided ameasuring system, particularly a microwave measuring system, for testinga material flow in the tobacco-processing industry for the existence ofat least one foreign substance and/or for detecting the weight, densityand/or humidity level of at least a section of the material flow. Themeasuring system is modified in that at least two measuring devices areprovided for measuring the material flow in space, in differentdirections relative to each other. In this case, the measuring directionmust be understood to be the direction of the field that is critical forthe measurement, particularly the electrical field. For this, at leastone measuring device is preferably designed such that a measuring in theconveying direction of the material flow is possible. German Patent No.198 54 550 A1 shows in this connection, a corresponding measuring devicethat permits a measurement in the conveying direction of the materialflow. One of the resonator devices according to the invention can beused, for example, as described in the above if at least one measuringdevice is designed to permit a measuring crosswise to the conveyingdirection of the material flow.

In a preferred embodiment of the invention, three measuring devices areadvantageously provided, wherein the measuring devices are designed suchthat the material flow can be measured in three different spatialdirections, relative to each other, in particular in essentiallyorthogonal directions. Very exact measurements and in particularmeasurements with a high local resolution are possible with a measuringsystem of this type. It is advantageous if the measuring device, whichpermits a measurement crosswise to the conveying direction, is one ofthe resonators according to the invention and described in the above.

According to yet another aspect of the invention, there is provided amethod for testing a material quantity, in particular a material flow inthe tobacco-processing industry, for the existence of a foreignsubstance and/or for detecting the weight, density and/or humidity ofthe material. For this, a first electromagnetic field is generated in afirst resonator and a second electromagnetic field is generated in asecond resonator, the material is moved through the first and the secondfield and a change in at least one characteristic of the electromagneticfield is measured.

The field intensity, the frequency or the phase, for example, canrepresent one characteristic of an electromagnetic field. In the case ofa stationary wave field, the position of the antinodes or the nodes orthe resonant frequency and the amplitude can furthermore represent onecharacteristic of an electromagnetic field, e.g. for a resonator.

The electrical fields are preferably oriented in different directionsrelative to each other. It must be assumed that the E field and the Hfield are oriented in different directions relative to each other. Aneven more exact analysis of the material flow based on the foreignsubstances or an even more exact detection of the density, humiditylevel and weight of the material flow is possible if a third resonatordevice is provided, which generates a third electromagnetic field. Thematerial quantity is moved through this third field, which is orientedin a different direction relative to the first and second field, and thechange in at least one characteristic of the third field is measured.

The electrical fields in the respective resonators are essentiallypositioned orthogonal to each other.

If the measured values are evaluated to generate an ejection signal, itis possible to separate out, for example, sections of the material flowfrom the further processing. As a result, it is possible to avoid theproduction of poorly filled cigarettes or cigarettes that are too dry orare composed of a foreign substance. The measured values from theresonators are preferably correlated, so that a very exact localresolution is possible. The rejection of conveyed material can be keptas low as possible with such an exact local resolution. Combining themeasuring results from the different resonators thus increases theaccuracy or the local resolution of the measurements.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in further detail in the following withexemplary embodiments and by referring to the drawings, whereinreference is made to the drawings for the disclosure of all details ofthe invention that are not explained in further detail. Shown are in:

FIG. 1 A view from above of a cross section through a resonator housing.

FIG. 2 A cross section through the resonator housing in FIG. 1, alongthe sectional line A—A.

FIG. 3 A cross section through the resonator housing according toanother exemplary embodiment of the invention.

FIG. 4 A cross section through the resonator housing in FIG. 3, alongthe sectional line C—C, in a view from the side.

FIG. 5 A schematic of a measuring device according to the invention.

FIG. 6 A schematic of a measuring device according to another embodimentof the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The same reference numbers are used for the same elements in thefollowing Figures, so that these elements are not presented anew.

FIG. 1 shows a view from above of a cross section through a resonatorhousing 4.1, wherein the view is along arrows B on the sectional lineB—B in FIG. 2. Only a few of the characteristics are shown in FIG. 1.Some of the characteristics shown in FIG. 2 were not drawn into FIG. 1for reasons of clarity. A hollow cylinder 6 of metal, preferablyprovided with a gold layer 12 at least on the inside, delimits theresonator housing 4.1. A post 19 is shown in the center of the hollowcylinder 6, which post is also coated with a layer of gold 12. Thehollow cylinder 6 and the post 19 are shown in a cross section. One viewshows a line resonator 21 in the inside space 7 or the cavity 7, whichis an open ring with two end faces 20. A through bore 10 through whichthe cigarette rope 1 can pass is also shown.

FIG. 2 shows a partially opened up cigarette rope 1 that moves in thedirection of arrow 5. The cigarette rope 1 consists of a filler material3 of cut tobacco and a wrapper 2 of cigarette paper. The cigarette rope1 extends through the resonator housing 4.1, to which microwave rays arefed for the purpose of detecting the weight, density and/or humiditylevel of the filler or for detecting the existence of a foreignsubstance in the filler. The resonator housing 4.1 has a cavity formedby the hollow cylinder 6, the inside space 7 of which is arrangedsymmetrical to the post 19. A lid 8 for closing is screwed to the hollowcylinder. The hollow cylinder 6 and the lid 8 consist of a material withvery low temperature coefficient. An alloy composed at leastapproximately of 64% iron and 36% nickel is suitable for this. Anexcellent constancy of the measuring results can be achieved owing tothe excellent constancy of the resonator housing 4.1 geometry.Contributing to this is also a temperature control for the resonatorhousing, indicated in FIG. 2, which uses a temperature sensor 9 todetect the temperature. The temperature sensor controls at least oneheating transistor 11, for example a type BUZ 80 by the Siemens Company,the dissipation heat of which advantageously heats up the resonatorhousing, preferably via the environmental temperature. The controlsystem itself is not shown in FIG. 2, but is known to the person skilledin the art.

A thin layer of gold 12 is deposited on the surfaces forming theboundaries of inside space 7 of resonator housing 4.1 and preferablyalso on the line sensor 21, which is an open ring in this case. Thisgold layer reliably prevents corrosion, which reduces the measuringvalue constancy, and simultaneously prevents a damaging side effect onthe skin owing to the high electrical conductance. The resonator housing4.1 advantageously is also gold-plated from the outside to preventcorrosion.

To prevent a soiling of the interior space 7 that would impair themeasuring result, a protective tube 13 that advantageously consists of asubstance of the poly aryl ether ketone (PAEK) group, e.g. poly etheraryl ketone (PAEK), is used to mechanically seal the interior space 7against the cigarette rope 1 and any dirt particles conveyed along. Theprotective tube 13 can be expanded in the shape of a funnel at one ofits ends, at which the rope 1 enters the resonator housing 4. Forreasons of clarity this is not shown in FIG. 2.

Outside of the interior space 7, the resonator housing 4.1 extends onboth sides in the shape of a tube toward the outside 14, in thedirection of rope 1, so as to prevent the microwaves from exiting theresonator chamber. The tubular section can also extend to some degreetoward the inside. However, this is not shown in FIG. 2.

A coupling-in antenna 17 that is insulated against the metal housing 4.1with an insulation 16 functions to couple in the microwaves generated bythe microwave generator. A coupling-out antenna 18 that is insulatedagainst the lid 8 with an insulation 16 serves to couple out themicrowaves, which are to be fed to an evaluation circuit, that is notshown herein. The aforementioned antennas 17 and 18 can also be arrangedon the same housing side. In that case, they are preferably arrangedoffset in circumferential direction. A suitable evaluation circuit isdisclosed in German Patent No. 197 34 978.1, which is thus acknowledgedin this application.

The invention makes it possible to provide a directional field withincreased energy density, which is particularly distinctive between thetwo end faces 20 or the field exit areas 20 of the line resonator 21,which is shown as an open ring for this exemplary embodiment. Thisresults in a very short or small measuring window that clearly increasesthe measuring sensitivity, in particular to foreign substances.

The line resonator 21 is arranged directly adjacent to the couplingantennas 17 and 18. Non-conducting fastening means are provided forfastening the line resonator and connecting the line resonator to thehousing. If a high-frequency electromagnetic alternating field emanatesfrom the open end of the coupling-in antenna 17, a stationary wave isexcited in the line resonator 21 through electrostatic induction. Thiswave takes energy from the coupling-in antenna 17 if the resonancecondition is met, meaning if the wavelength of the stationary waveharmonizes with length L of the resonator. That is the case if thefollowing applies: L=n×X/2, wherein n is a whole number. The stationarywave in the line resonator, in turn, excites through electrostaticinduction an electromagnetic wave in the coupling-out antenna 18, whichdrains the energy from the resonator. A capacitive coupling wasdescribed in the above. However, within the framework of this invention,an inductive coupling is possible as well.

A potential antinode of the stationary wave is present at the open ends20 of line resonator 21. The polarity of the internal surfaces is thesame in this case if n is an even number and is opposite if n is an oddnumber. In the latter case, a concentrated electrical field is generatedbetween the end faces, which extends through the bore for the cigaretterope. As a result, the dielectric properties of the goods to be measuredexert a particularly high influence on the resonator behavior and thuslead to an effective detection of foreign substances.

FIG. 3 shows another exemplary embodiment of the present invention. Incontrast to the previous embodiment shown in FIGS. 1 and 2, a hollowcube 22 is used as resonator housing 4.2 and metal strip forms the lineresonator 21. FIG. 3 shows a sectional representation along the line D—Din FIG. 4, wherein this section is viewed in arrow direction. FIG. 4 isa view from the side of a sectional representation along the line C—C inFIG. 3. The additional features such as the protective tube 13, the goldlayer 12, the cigarette rope 1 etc. are not shown in these Figures, soas to provide a clearer view of the elements shown.

The backplate electrode for the field exiting from the line resonator 21or the end face 20 or from the field exit area 20 is theopposite-arranged housing wall, which functions there as groundelectrode.

The exemplary embodiments according to the invention, described herein,are particularly suitable for realizing a method for testing aproduction material in accordance with German Patent Application 101 00664.0. The content of this patent application is incorporated byreference into this application. The same is true for the content of theGerman Patent No. 198 54 550 A1 and the content of German PatentApplication 197 34 978.1.

The method for testing a production material in accordance with GermanPatent Application 101 00 664.0 in particular is used for testing largequantities of tobacco that are automatically processed in thetobacco-processing industry, in particular to check for foreignsubstances that may be present in the cigarettes. These foreignsubstances can effect the production quality, e.g. appearance, taste andwear values. A microwave field is generated for this, the material ismoved to the effective range of the microwave field and the influence ofthe microwave field is analyzed, wherein the actual values of a firstand second characteristic variable of the microwave field are measuredsimultaneously. A permissible value range is specified for these actualvalues and a check is made to determine whether these actual values arein the permissible value range. A signal is generated in those caseswhere the actual values are not in the permissible value range.

The permissible value range in this case includes variable values thatoccur when the microwave field is influenced by a material quantity,particularly a cigarette rope that contains exclusively the productionmaterial. The material flow in this case is preferably divided intosections prior to or following the passage through the effective rangeof the microwave field. Sections, which generate the signal during thepassage, are then removed from the material flow. The permissible valuerange can be determined by guiding a reference amount of the productionmaterial, which does not contain foreign substances, through theeffective range of the microwave field. The actual values measuredduring the passage of the reference amount then form the permissiblevalue range. The material for the reference amount can advantageously bewrapped with a wrapping material.

This process can advantageously be realized with an additional method,in which at least one characteristic of the production material isdetermined parallel and independent thereof from the actual values ofthe same characteristic variables of the microwave field. Thischaracteristic in particular can be the density, the weight and/or thehumidity level of tobacco used as production material.

Metals and plastic materials are primarily considered as foreignsubstances, which physically cause a totally different change in themicrowave field than the water-containing tobacco material. The highconductivity of the metals causes a strong reflection or scattering ofthe microwaves. Plastic materials have noticeably different dielectricnumbers and loss factors as compared to tobacco, so that these can alsobe detected easily.

With this method, different frequencies are preferably supplied to theresonator, wherein the transmission capacity for these frequencies isdetermined and the two variables or several characteristic variables aredetermined from these data with the aid of a mathematical method.Resonance curves are preferably used for this and corresponding variablepairs are determined, which are measured around a median frequency dueto the insignificant detuning. Further details may be gleaned fromGerman Patent Application 101 00 664.0.

The materials and coatings used for the exemplary embodiment accordingto FIGS. 3 and 4 can be the same ones used for the exemplary embodimentaccording to FIGS. 1 and 2.

FIG. 5 schematically shows a measuring device according to theinvention, comprising three resonators housings 4.3-4.5. A cigaretterope 1 filled with a filler 3 passes through the resonator housings4.3-4.5. A paper strip 2 is furthermore wrapped around the filler 3. Theresonator housings 4.3-4.5 contain cavities that are not shown herein.Electromagnetic fields are generated inside the cavities, which havedifferently oriented electrical field lines 23. Thus, the field lines 23in the resonator housing 4.5 on the right side of FIG. 5 extend inconveying direction 5. The field lines 23 inside the resonator housing4.4 in the center of FIG. 5 extend crosswise to the conveying direction5, in the drawing plane, while the field lines 23 inside the resonatorhousing 4.3 on the left side extend crosswise to the conveying direction5 and out of the drawing plane. In one preferred embodiment shown inFIG. 6, a single main housing 4 comprises the plurality of resonatorhousings 4.3-4.5.

If the field penetrates the filler 3 or rope 1 to be measured indifferent directions, each additional direction provides additionalmeasuring information. Measurements are preferably taken in two or eventhree directions, which can be in the movement direction as well asperpendicular to it. This permits the detection of many foreign bodies,which would not be detected, for example, with a measurement exclusivelyin one direction.

The measuring signals can subsequently be evaluated separately, so thatan ejection occurs if at least one of the sensors or measuring devicesdetects a foreign body. However, the measuring signals can also belinked to improve the local resolution or increase the generalsensitivity of the system. The measurements are offset in time as aresult of the distance between the resonator housings, the productionspeed or the conveying speed for material to be tested and can thus becompensated easily through calculations.

The invention has been described in detail with respect to preferredembodiments, and it will now be apparent from the foregoing to thoseskilled in the art, that changes and modifications may be made withoutdeparting from the invention in its broader aspects, and the invention,therefore, as defined in the appended claims, is intended to cover allsuch changes and modifications that fall within the true spirit of theinvention.

What is claimed is:
 1. A resonator device for testing a materialquantity in the tobacco-processing industry for existence of at leastone foreign substance and/or for detecting at least one of weight,density and humidity level of the material, comprising: a resonatorhousing having a through opening for the material to pass through and atesting region located inside the resonator housing to which thematerial can be moved at least in part; and at least one element thatincreases energy density of electromagnetic waves for increasing theenergy density in at least a portion of the testing region, wherein theelement is a line resonator with at least one end face that functions asan electrode, and wherein the line resonator has two end faces thatfunction as electrodes and which are oriented toward the testing region.2. The resonator device according to claim 1, and further including acoupling-in antenna and a coupling-out antenna connected to the housingfor coupling electromagnetic energy into and out the housing,respectively.
 3. The resonator device according to claim 1, wherein theresonator housing has a wall delimiting a cavity of the resonatorhousing and the element is positioned inside the cavity at a distance tothe wall.
 4. The resonator device according to claim 1, wherein the atleast one end face is arranged near the testing region.
 5. The resonatordevice according to claim 1, wherein the testing region has across-sectional surface that is positioned essentially parallel to theend face and the end face has a size that is smaller than thecross-sectional surface of the testing region.
 6. The resonator deviceaccording to claim 1, wherein the two end faces are ranged on oppositesides of the testing region so that the material can be moved through aspace between the end faces.
 7. The resonator device according to claim1, wherein the line resonator is an open ring.
 8. The resonator deviceaccording to claim 1, wherein the two end faces are positionedessentially parallel to each other.
 9. The resonator device according toclaim 1, wherein the at least one element is comprised at least in partof a material with a low expansion coefficient.
 10. The resonator deviceaccording to claim 1, wherein the at least one element is coated with acorrosion-resistant material.
 11. The resonator device according toclaim 10, wherein the corrosion-resistant material is comprised at leastin part of a corrosion-resistant metal.
 12. The resonator deviceaccording to claim 1, wherein the resonator device comprises a microwaveresonator.